The Timing category covers engine timing-system parts responsible for synchronising valve operation with piston movement. You will find timing belts (toothed), timing chains, automatic and manual tensioners, guide rollers, camshaft sprockets and timing repair kits.
A snapped timing belt in an interference engine causes pistons to strike valves — a costly failure requiring a cylinder-head rebuild. Timely replacement of the belt or chain per the manufacturer's interval is one of the most important engine maintenance tasks.
Every 60,000-120,000 km or every 5-7 years — depending on the engine manufacturer. Rubber ageing occurs even without mileage, so the time interval is as important as the distance one. When replacing the belt, always replace the rollers and tensioner.
A chain is more durable (200,000+ km) but more expensive to replace and noisier. A belt is quieter and cheaper but requires regular replacement. The choice depends on the engine design — one cannot be swapped for the other.
Engine rattling at cold start (the chain slackens when cooled), cam/crank correlation fault codes, increased fuel consumption and rough idle. Measuring chain stretch requires a specialist tool or computer diagnostics.